Draft-controlling device for furnaces



Feb. 6, 1923. 1,444.523. J. H. PRESCOTT.

FILED JULY 28,1919- I 2 SHEETS-SHEET I.

Feb. 6, 1923.

J. H. PRESCOTT. DRAFT CONTBOLUNG DEVIQE FOR-FURNACES.

2 SHEETS-SHEET 2 FILED jun 28.1919

Patented Feb. d, i923.

JESSE H. PRESCOTT, OF MEDEDBD, MASSACHUSETTS, ASSIGNOR TO WILLIAM: K. LOGEE OF PROVIDENCE, RHODE ISLAND.

DRAFT-CONTEOLLING DEVICE FURNi-LCES.

Application filed July 28, 1919.

To all whom it may concern:

Be it known that 1. Jesse H. ltnnsco'r'r, a citizen of the United States. residing at llledford, in the county of Middlesex, State 5 of Massachusetts, have invented certain new and useful Improvements in Draft-Controlling Devices for Furnaces, of which the following is a specification.

My invention is an improved apparatus for controlling the forced draft of steamboiler or other furnaces. whereby the current of air, or air and steam, is automatically shut off when the firing-door of the furnace opened; and immediately supplied again upon the closing; of the door. Through this automatic control of the forced draft flareback through the firing-doors is avoided, and more important. the fine particles of partly consumed fuel are prevented from being blown up the fine and wasted; while the temperature in the combustion chamber or the box is maintained more nearly at maximum by preventing the cooling oil of the fire under a sudden inrush of air.

vide a simpler and more etlicient apparatus for the purpose above described, which may be applied to practically all. types of fun,

naces without material change or alteration in the organization thereof, and which when once installed will operate automatically without adjustment or other attention. A further object of the improvement is to render the device operative from the movement of the firing-doors of the furnace without the need of other motive power, and without requiring electromagnetic or other complicated actuating means.

The manner and means for carrying out these improvements are fully described in the following specification. illustrated by the accompanying drawings, in which like refereure characters indicate like parts. In the drawings Fig. l is a front elevation of a steamlioiler furnace. showing my improved draftcontrolling device applied to use thereon;

Fig: 2. an enlarged detail view of the opcrating; mechanism for the shut-off valve of the draft-blower;

Fig. 3. an elevation of the balanced weighted lever which furnishes the power to. operate the shut-off valve;

The object of my improvement is to pro- Serial No. 313,736.

Fig. 4, a detail view of the crank-connection between the tiring-door and weighted lever; and

Fig. 5. a view in reduced scale showing a modified arrangement of the connections between the liring-door and valve-operating lever.

Referring first to Fig. 1. A designates the boiler front which is usually set in masonry M, while beneath the boiler are two firingdoors F B and two lower ash-pit doors E--E. At the side of the boiler furnace, or arranged in other convenient location, is a power-actuated blower B or forced draft appliance which communicates with the ashpit to SUPPLY a current of air beneath the furnace grate. The blower B may be of any suitable construction usually employed for this purpose and is preferably driven by steam pressure from the boiler, although it might be operated from any other source of power such an electric motor. The blower B may operate on the suction fan principle or with a jet of steam. its detail of construe tion not being: shown in the present drawings since such types of apparatus are well known to those versed in the art. Sutlice it to state that the blower B operated under steam pressure comu'mnicated through a pipe P connected thereto at p and communicating with the boiler at any convenient point, not herein shown. The steam pressure in the pipe P is regulated by an overhead valve V which is controlled throuoh a system of cords and pulleys, as indicated at leading to the main damper in the flue at the rear of the furnace. These connections, however, not being essential to the operation of the present apparatus are not herein described and illustrated in detail.

the side of the boiler is a hand-valve H for manual control of the steam pressu're supplied through the pipe P to the blower ii. and just below the hand-valve is the auto matically operated shut-off valve K. As shown more particularly in Fig. the valve l; is of the well known balanced type having); two opposite ports 2 and 3 adapted to be closed by or plugs i and 5 carried by a sliding stem 6. The stem 6 is operated from a lever 8 having: its lower end pivotallv connected at 9 to a link 10 which is hinged to the side of the valve casing. iibr its pivot 9 the lever 8 is connected to a yoke 11 on the end of the stem 6 and is guided in its movement between the ends of a forked arm 12 rigidly supported from the valve casing. Pivotally connected to the upper end of the lever 8 by means of a yoke 14 is a horizontal rod 15 which is operated from the balanced weighted lever 16. The weighted lever 16 is preferably arranged within a segment-shaped casing or box 17, see also Fig. 3, to protect it from accidental displacement and prevent interference with its action, the casing being conveniently located on the front of the boiler or its setting as illustrated in Fig. 1. Closing the front of the casing 17 is a removable cover-plate 18 held in place bysuitable screws 19. On the rear wall of the casing 17 is a boss 20, see Fig. 3, from which projects a stud 21 providing the fixed pivot for the weighted lever 16 which is formed with a hub 22 bored to receive the stud. The main arm of the lever 16 extends upwardly from its hub 22 and carries the cylindrical weight 23 at its upper end, while below the weight is a cylindrical-headed stud 24 reaching through the arm and held in place thereon by a pin 25 at its rearward end. The head of the stud 24 is formed with a transverse bore 26 through which the rod 15 is loosely inserted. As shown in Fig. 2, the rod 15 is screw-threaded froi'n its outer end throughout the greater part of its length, and on opposite sides of the stud 24 are stop-nuts 27 and 28 screwed onto the threads. The nuts 27 and 28 are arranged in pairs so that one may be set up against another to lock them in place in the manner of check-nuts. As before indicated, the rod 15 is free to slide through the bore of the headed stud 24 when the weighted lever 16 is moved from one position to the other as indicated by the full lines and dash lines in Fig. 2. When, however, the stud 24 comes into engagement with either set of nuts 27 or 28 on the rod 15 the latter will be moved by the weighted lever 16 to operate the lever 8 to open or close the valve K, as the case may be. The nuts 27 and 28, being adjustable along the rod 15, provide for setting the mechanism so that the valve action takes place only at the extreme end of the throw of the weighted lever 16 in either direction.

The weighted lever 16 is shifted across the vertical plane of its axis of rotation, by means of a rockable bell-crank lever 29. The bell-crank 29 acts on the weighted lever 16 to initiate its movement to carry it across center, whereupon its motion is continued solely through the action of gravity. In this way the weighted lever is caused to act on the valve-lever 16 by gravity to secure a quick closing or opening of the valve. there being lost-motion between the weighted lever 16 and the actuating rod 15 as provided for by the sliding of the rod through the stud 24. The bell-crank 29 is provided with a hub 30 pivoted on the outer end of the stud 21, and held in place by the cover 18 of the casing 17. Projecting from the left-hand side of the hub, as viewed in Fig. 2, is a horizontal arm 31, from the end of which is suspended a counterweight 32 which tends to normally maintain the bell-crank 29 in the position shown by full lines in Fig. 2. The arm 31 is continued across the top of the hub 30 in the shape of a quadrant having its central portion cut away to form two spaced, upstanding lugs or contact-shoulders 33--34. The shoulders 33-34 are adapted to engage the sides of a lug 35 which projects from the front of the arm of the weighted lever 16. It will thus be seen by reference to Fig. 2 that when the bell-crank 29 is rocked in either direction it acts through one of the shoulders 33 or 34 to shift the weighted lever 16 across center, after which the latter is free to be movedby gravity until its lug 35 strikes the opposite shoulder on the bell-crank.

The bell-crank 29 is connected to be operated from the firing-doors F-F of the furnace by means of a horizontal rod 36 which is connected to its vertical arm 37. Referring particularly to Fig. 3, the hub 30 of 9 the bell-crank 29 carries a stud 38 projecting through an opening in a boss 39 on the front of the cover 18 of the casing 17. The outer end of the stud 38 is squared off on its sides, see also Fig. 2, and fitted to a square bore in the hub 40 of the arm 37. A washer 41 is held against the outer end of the hub 40 by a screw 42 screwed into the stud 38 to secure the arm 37 fast with the main hub 30 of the bell-crank with the inner end of the hub 40 bearing against the boss 39. At its lower end the arm 37 is pivotally connected to a yoke 43 on the end of the connecting-rod 36 which extends across the front of the boiler above the firing-doors F F. The rod 36 is slidable through bearings 4444 on the sides of two casings 4545 which are attached to the boiler front 13 above the hinges of the firing-doors F-F as shown in Fig. 1. Each casing 45 is provided with a bearing 46 on its bottom in which is journaled a vertical shaft or rod 47, see Fig. 2. carrying a crank-arm 48 at its upper end. At the end of the crank 48 is a stud 49 on which is journaled a roller 50 adapted to engage with and ride along the face of a cam-plate or crosshead 51 secured on the connecting-rod 36 and extending laterally thereof as shown in Fig. 4. The shaft 47 forms an extension of and is connected to the upper end of the hinge-rod 52 of the firing door F by means of a coupling 53 shown in Fig. 2. This latter consists of two collars 54-54 keyed to the ends of the two rods 47-52 or secured thereon by set screws 55 and having a key and slot connection 56 at their ends. Through this arrangement the rods 47-52 are connected to be rotated tonether from the movement or" the firing-door F", the rod 52 being held fast in the hinges ff of the latter by splines or set-screws 5?, see Figs. 1 and 2. It has been explained that there are two casings 4:5, one above each firing-door, and their arrangement and connection with the hinge-rods 52 are substantially the same. The operating rod 86 may extend continuously between the two casings, but is preferably formed. of sections connected by turnbuckles or adjustingnuts 58-58 as shown in Fig. 1. This arrange ment allows for adjusting the length of the rod in accordance with variations in the distance between the door-hinges and also pro-- vides a more or less flexible connection be tween the end-sections of the rods to take care of inaccuracies in the alineinent of the bearings. The rod 36 may be extended for connection with any number of firing-doors and, preferably, it carries a collar 62, see Figs. 2 and 4, which is adapted to strike against the bearing 44 on one o? the casings 4:5 to limit the sliding movement of the rod to the right.

Fig. 4 of the drawings shows the righthand casing 45 with the crank-motion for the right-hand firing-door F and, as before stated, the arrangement of the left-hand casing for the door F is the same. It w' l be noted from Fig. 4 that normally, wi the firing-door closed, the crank-arm 4:8 as snines a position in alineinent with the connecting-rod 36 as shown by the tull lines in this view. Therefore, when the door F swung outwardly on its hinges to open it it will rotate the rod 52 and shaft ll'to turn the crank 4-8 inwardly toward the boiler. as indicated by the dash lines in Fig. l. This action causes the roller 50 at the end of the cranloarm 48 to come into engagement with the side or" the crosshead 51, and riding there along it will slide the connecting-r .l 36 to the left as indicated, by the dash lines in Fig. 4. The same action takes place when the left-hand firing-door'F is swung open on its hinges, except that in this case the cranlo arm lS turns outwardly away from the boiler, but its effect on the crosshead 51 is the same and the rod 36 will he slid to the left.

Fig. 5 illustrates a modification in the arrangement for connecting the sliding rod 36 with the bell-cranlr 30 which operates the weighted lever 16. In some cases. where tlw automatic shut-oil" ralve for the steam pres sure blower B is located at the letthand side of the boiler it is necessary to reverse the direction of action of the controllinnmechanism. For this purpose the slidingconnecting-rod 36 may be arranged to move to the right by reversing the position of the crank-motion parts, and the end ot the rod is then connected. to the horizontal arm 31 of the bell-crank 29 by means of a cord or chain 60 passing over a pulley 61. This mode or connecting the slide rod 36 with the weight-operating means may also be employed where the blower is located in a more remote position, around a corner or at higher lower level than the door-operated means. In other instances. where the doors are hinged to swing on a horizontal axis their crank-motions may be arranged to operate a vertically slidable rod connected to the arm 31 ot' the bell-crank 29.

The method of: operation of the complete apparatus as follows: The device may be applied to use on practically all types of turnaces using; forced draft and its me -iis1n y be installed without matefal lit alteration of the original plant. i ll required to brealr into the steamwith the dlllffilflr tic shut-off valve 1, and to attach the controlling mechanism to the 1 ot the boiler in connection with the ooors F-JT. l i ith the apparatus inin manne as above lcscribed the i *n operates as next explained:

either oi the iiiri is opened tor any purpose, as "for inspec stoking; or ralringg the fire. the turning (it its hii'ig'es will cause tile hinge-rod I39, and its to be re t DIE-ClOOFS F- The rota- 0 against the croesheail '-rod 36. .lt will be no ed the dra wi that the e o connr ..i

52 and 4: o

s amount of lost-motion between the (runs 4 and the crossho -ul 51 so th t the woo." limited onto 1 may be ouened to 1 r oher o0 starts to act on lie crossheai'l m head. alone he rm t o to regu ate the anmunt of this lost-motion and usually it is set so that u ter the door has seen swun o n to an appreciable 20 I and, a

pivot 21 .4 the bell-crank rection indi i. s contact-shu Bil; bear as; Hi. wll mine dire tioit.

s continued liv o D I l 099111119 oi until l il or c we: 1 across the ioal iilanc as it drops to the position indicated by the dash lines in its stud 2+5, sliding along the rod 15, strikes against the stop-nuts 2t and thereby moves the rod to the right. This movement of the rod 15 causes the valvecontrolling lever 8 to be swung to the rig rht to slide the valve-stem 6 into the casing of the valve K to close the gates t and 5 against its ports. in this way the valve K is closed with an abrupt action to shut off the steam pressure from the blower P so that the latter will cease to function. The weighted lever 16 continues to act 'irough gravity to maintain the valve K cio ed as long'as either of the tiring-doors remains open, and hence the forced draft is cut off so that it cannot cause a flare-back through the door. hloreover, the shutting off of the draftprevents the line particles of fuel which are under partial combustion from being blown up the tine, due to the sudden inrush of air through the firing-door. In this n L, the device not only provides a measure of safety in the operation of the furnace, but, furthermore, and more important it is of material benefitin con serving fuel and saving steam. by preventing the sudden cooling of the tire.

When the inspection or tendingof the tire is completed the closing of the door acts to again start the operation of the blower in the manner as next explained: its the door l or F is swung to on its hinges the rod and its connect-ed shaft i! a re rotated to turn the crank-arm 48 back to first position,

as illustrated y the full lines in Fig. l. This action relea the pressure of the roller :31) against the crosshead 51 and the rod 36 is thereby allowed to slide to the right under the impulse of the counterweight 32 on the arm 31 of the bellrent: 29. It will be notiul from reference to Fig. 2 that the counterweight 32 has a gre leverage on the bellcrank 29 then that of the weighted lever 16, whereby the latter i moved from the counterweight to swing it to its mid position. That is to say, the engagementof the shoulder 341- on the bell-eranlr 29 with the lug 35 on the weighted lever 16 causes the letter to be swung to the left under the uction of the counterweight ll hen the weighted lever 16 is thus shifted across the vertical plane of its axis the force of gravity once more comes into play to cruise it to swing into first position as illustrated by the Full lines in Fig. is the lever 16 drops to this position its lug 35 strikes against the contactshoulder 33 on the bell-cranl' 2.) to prevent it from. further mo .'eineut, the movement of the bell-crank 29 under the action of its weight 252 being limited by the rod 36 as controlled by its stop-collar 152 before de scribed.

li 'leanwhile, as the .'eighted lever 16 swings back to illSt oosition its stud. .Z-l

brings up against the StOP-IHULS 21 on the rod 1 and acting therethrough moves the rod to the left to swing the lever 8 in the same direction. This latter act-ion causes the valvestem 6 to be slid to the left to withdraw the plugs 4 and 5 from the ports of the valve K so that the latter is opened by a quick movement to admit the steam pressure to the blower B. In this waythe blower is caused to function again to supply the forced draft to the tire immediately the firing-door is closed.

It will be observed that the mechanism of my improved device is extremely simple in construction and method of operation, emcient in action, and proof against derangement or getting out of order. It may be applied to use with practically all types of forced draft furnaces without reconstruction or rearrangement of the parts thereof and when once installed operates automatically without adjustment or setting. It is further to be noted that the device is operated from the movement of the firing-doors without the need of motive power, other than the gravity of its balance weight, yet its action is quick and positive in opening and closing the steam pressure valve which supplies power to the blower. i

Various modifications might be made in the structure and arrangement of the parts of my improved device without departingfrom the spirit or scopeof the invention; therefore, without limiting myself to the precise embodiment herein shown and described, what I claim is:

1. .ln a draft-controlling device for furnaces, the combination with means for supplying forced draft to the fire, of means to arrest the draft, a pivoted Weighted lever for operating the draft-arresting means, and means operated by the opening of the firingdoor to shift the weighted lever across the vertical plane of its axis of rotation to cause it to act through gravity to operate the draft-arresting means.

2. In a draft-controlling device for furnaces, the combination with a blower for supplying forced draft to the fire, of means for operating the blower, means to stop the action of the blower, a pivoted weighted lever for actuating the stopping means, and means operated by the opening of the firingdoor of the furnace to shift the weighted lever across the vertical plane of its axis of rotation to rinse it to act on the stopping means by gravity.

3. In a draft-controlling device for furnaces, the combination with a power-operated blower for supplying forced draft to the fire, of means for starting and stopping the blower, a pivoted weighted lever controlled by gravity to operate said starting and stopping means, and means connected to the firing-door of the furnace to shift the weighted lever across the vertical plane of 1 ssess the blower when the door is opened and to start the blower when the loor is closed again.

4:. In a draft-controlli11g device for fun naces, the Combination with a steam pressure operated blower for supplying forced draft to the fire. of a valve for controlling: the operation of the blower a gravity-com trolled pivoted weighted lever for operating the valve, and means connected with the hi"- ing-door of the furnace to shift the weighted lever across the vertical plane of its axis to cause it to close the valve when the door is opened and to open the valve when the door is closed again.

5. In a draft-controlling device for furnaces, the combination with a power-actuated blower for supplying forced draft to the fire, of means to control the power to start and stop the blower, a gravity-actuated pivoted weighted lever for operating the power controlling means, and means oper ated from the openin and closing of the firing-door of the furnace to initiate a movement of the weighted lever in one direction or the other whereby the force of gravity will cause it to act on the power-controlling means to stop or start the blower.

6. In a draft-controlling device for furnaces, the combination with a power-actuated blower for supplyingforced draft to the fire, of means for controlling the power to start and stop the blower, a pivoted weighted lever for actuating the power-controlling means, and means operated by the opening and closing of the firing-door of the furnace to shift the weighted lever across the vertical plane of its axis to cause it to act in opposite directions through gravity to actuate the power-controlling means.

7 In a draft-controlling device for furnaces the combination with a power actuated blower for supplying forced draft to the fire" of means movable in opposite directions to start and stop the blower, a pivoted weighted lever arranged to act through gravity to shift said starting and stopping means and means operated from the opening: and closing of the firing-door of the furnace to iniQate the movement of the weight across the vertical plane of its axis to shift it into position to be further actuated by gravity:

8. In a draft-controlling device for fun naces, the combination with. a blower for supplying forced draft to the fire. of means shiftable in opposite directions to start and stop the blower, a pivoted weighted lever for shifting said starting: and stopping means, and means operated fron'i the opening: and closing of the firing-door of the furnace to throw the weighted lever across the vertical plane of its pivotal axis to cause it to be acted upon by gravity to operate on the starting and stopping means.

f forceejl r it to the fire of means llitililt'i. we ghted lever shift-able in opposite diroctwins to engage an d stops to move the memstops on d meinhon ai pivoted her. and means operated from the opening an closing; of the firin'ndoor of he furnace to throw the wein the vertical pla 1e of its where it will act on ;-member by gravity.

a draft-controlling device for furnaces. the combination w th a draft appliance for supplying forced draft to the fire, of means to control the operation of the dr ft appliance a era vity-controlled pivoted hted lever for eratinrr the draft-conmeans" a bell-crank :ecl lever across the m is to cause it to be gravity to operate the starting an d stoppinq means and means for connecting the hellcrank to be operated from the opening and closing movement of the firing-door of the furnace.

ll. ln a drafhcontrolling device for furthe J comb ne-ion with forced draft a of means to control the operation of the draft appliance a e avi v-controlled pivoted weir... ed lever for operating the 'twmitrollino means a hell-crank cond to be opera ed from the ooenino: and inc moven'ient of the firina-door of the and means conne tinn' the hellt the weighted lever to shift the as the vertical. plane of its sar s while allow n o' lo-stanotion therebe ween ;to cause the .t d lever to act on he drafbcow trol iw means by l9. in a. dra co dovim; Fmfnrnaces. the combination Wl. means for supplying forced draft to the ire, of means for starting: and stopping the operation of the draft-supplvian means. pivoted weighted lever for operating? the startingand stopping means. a slidable member for sh fting said weighted lever in oppos te dim tions to ause i to be nrther actuated hv and a cranle rated hr ement of the tin I s. ide the weightshi a draft-contiv llineice or for paces, the combination with means for sun plying; forced draft t the tire. of means for starting? and stopping the operation of the draft-supplying means a pivoted weighted lever for operating the starting; and stoppine means. a slidable member or sbiftino sad weighted lever acr ss the vert cal plane of its axis to cause it to be operated upon by ,a'ravity a crosshead on saidmemberi and a crank connected to he from the movement of the firing'door of the furnace to engage the crosshead to slide the shifti n e n l ember.

H. in a draft-controlling device for furnaces. the combination with means for supplying forced draft to the fire, of means for starting and stop jiing the operation of the draftsiipplying means. a pivoted weighted lever for operating the starting and stopping means a bell-crank having opposed contactshoulders for engaging; the weighted lever to shift it in opposite directions while allowing lost motion therehetween, and means connected to the tiring-door of the furnace to rock the bell-crank to shift the weighted lever across the vertical plane of its axis whereby it is acted upon by gravity to operate the starting and stopping means.

15. In a draft-controlling device for furnaces t 1e con'ibination with means for supplying forced draft to the tire of means for starting and stopping the operation of the draft-supplying means, a pivoted weighted lever for operating the starting and stopping means a bell-era k for shifting the weighted lever across the vertical plane of its axis, a connecting-rod for rocking the bell-crank, a crosshead on said rod, and a crank-arm operated by the movement of the firinggr-door of the furnace to engage the crosshead to slide the connecting-rod.

16.. An automatic draft-regulat 11g device for furnaces conuurisinry a draft-controlling member. a pivoted weighted lever adapted to be shifted across the vertical plane of its axis to cause itto act b v gravity on the controlling-member. and means operable from the movementof the firing-door of the furnace to initiate the movement of the weighted lever against the action of gravity.

17. An automatic draft regulating device for furnar comprising: a pivoted weighted lever a draft-controlliia; member movable from said. weighted lever, adjustable stops on said controlling-mcmber, means on the weighted lever for ei'rgaging said stops. and means operable fronithe movement of the tiring-door of the furnace to swing the weighted lever across the vertical plane of its axis to cause it to engage the stops on the controlling-member to operate the latter by g'avity.

18. An automatic draft-regulating device for furnaces comprising a steam pressure shut-off valve, a controlling-member for operating said valve, a pivoted weighted lever adapted to operate on said controllingmemher under the 'action'of gravity to open and close the valve and means operable from the movement of the firing-door of the furnace for initiating the movement of the weighted lever across the vertical plane of its axis whereby it is caused to act in opposite directions on the valve-controlling; member.

19 An automatic draft-regulatingdevice for furnaces comprising" a draft-controlling member, a rod connected to move said controlling-member, stops on said rod, a pivoted weighted lever movable across the vertical plane of its axis to engage it With the stops on the rod, and means adapted for connec tion with the firing-door of the furnace to shift the weighted lever in opposite directions.

20. San automatic draft-regulating dei 'ice for furnaces comprising a draft-controlling" member. a. pivoted Weighted lever for acting by gravity on the controllingnrember, a bell-crank having means for engaging the weighted lever to shift the latter in opposite directions across the vertical plane of its axis. a connecting rod for operating the bellcrank. and means adapted for connection with the firing-door of the furnace to slide the rod from the movement of the (l()01- In testimony whereof I afiix my signature.

JESSE H. PRESCOTT. 

